Mycorrhizal CLE mimicry

Abstract

Since the discovery of systemin in tomato in the past century, small peptides have become ubiquitous in plant signalling pathways. Various families with increasingly funny names each contain dozens of individual peptides: PEP, RALF, CEP, IDA, PSK, PSY, SCOOP, SCREW and so on. The CLE family (named after CLV3 and ESR) consists of secreted peptides that are 12–14 amino acids in length, which are perceived locally or systemically by leucine-rich repeat receptor-like kinases. They are broadly involved in many biological processes: maintenance of the shoot and root meristems, vascular development, senescence, nutrition, stomatal patterning, flower and fruit development, and stress responses — the list continues to increase.

CLE peptides also have a role in plant–microbe interactions, including during symbioses. A recent study in the Proceedings of the National Academy of Sciences USA, which comes from the Salk Institute and is led by Lena Maria Müller, identifies a positive role for CLE16 from Medicago truncatula during arbuscular mycorrhizal (AM) symbiosis, with an interesting twist: the AM fungus itself produces a CLE16 mimic to facilitate colonization.